Biological Explanations of Anorexia - Evolutionary Behaviours

1) Argues AN evolved because in certain situations it would have helped early humans survive.

3) During a famine there would be 2 possible responses; focusing on hunger and looking for food in the immediate area or ignoring hunger, becoming hyperactive and fleeing the area.

2) Anorexic traits such as high levels of activity and denial of hunger, would have been adaptive as they would have enabled people to flee famine.

4) Guisinger argues the second response would have been more adaptive and it sit this that anorexic behaviours would encourage.

5) She argues that humans have evolved to develop anorexic once they reach a low weight. During evolution this would have been due to famine, but now it is often due to dieting. This is called the adapted to flee famine hypothesis

+Other species have evolved anorexic like behaviours to enable them to mate or rear young. Eg Carrie Arnold points out that emperor penguins stop eating and lose up to 1/3 of their weight while looking after their young. If these species have evolved anorexic like behaviours because they are adaptive, it is possible humans have as well

+Guisinger aruges that birds have evolved periods of hyperactivity to deal with migration which is known as migratory restlessness. She argues that the hyperactivity often shown by anorexics could be seen as a form of migratory restlessness.

It is as if when the body loses enough fat (in the past due to famine) a 'hyperactive' switch is turned to enable the person to move and flee the situation

-Animal research might be relavant to humans; no reason to believe humans evolved the same way as birds have. Highly likely human behaviours are shaped more by social and cultural factors than those of other animal species

Surbey - Reproductive Suppression Hypothesis

1) Argues that anorexic behaviours have evolved because they would have been adaptive during evolution

2) If young females had tried to mate or reproduce during times of stress such as famine and migration this would have endangered their health and that of their young.

3) Anorexic behaviours such as weight loss suppress reproductive behaviour during these times of stress, so hey wouldn't try to reproduce. This is called the reproductive suppression hypothesis

+Similarly some species delay puberty or suppress reproduction in females if they are under stress or are in poor physical condition which supports RSH

-There is no direct evidence in relation to humans and they don't explain why anorexics refuse food even when it is readily available and there are no stressers in the environment; trait wouldn't be adaptive

-Not all anorexics show hyperactivity which is an important part of Guisinger's theory. Also 10% of anorexics are male, which is hard to explain for Subey's theory.